Dark Fishing Spider, Dock Spider
Dolomedes tenebrosus
Pisauridae (Nursery Web Spiders), Order Araneae. Key family characteristics include the ability to walk on water and carrying the egg sac in the chelicerae until just before hatching.
Physical Description
Robust body with a flattened profile designed for pressing against vertical surfaces and tree bark. The cephalothorax is broad and rounded, while the elongated oval abdomen is slightly pointed at the rear. The body is covered in fine, velvety hairs providing exceptional camouflage.
Size Estimate
Body length ranges from 15 to 26 mm for females and 7 to 13 mm for males, with a formidable leg span reaching up to 70 to 90 mm. This specimen appears to be an adult or sub-adult.
Coloration & Markings
Mottled pattern of grayish-brown, dark brown, and black, featuring distinct dark W-shaped or chevron markings down the center of the abdomen and alternating dark bands on the long legs, offering supreme cryptic camouflage against rough tree bark.
Web Type
None. This species does not build webs to capture prey; instead, it is an active hunting wandering spider.
Eye Arrangement
Eight eyes arranged in two distinct, slightly curved rows of four. The eyes are relatively equal in size compared to wolf spiders, which helps distinguish pisaurids from lycosids.
Leg Characteristics
Long, powerful legs extending laterally in a crab-like or sprawling posture when resting, heavily banded with dark rings and equipped with numerous spines and claw tufts to grip rough surfaces and navigate water surfaces.
Venom & Safety Information
Venom Information
Neurotoxic and proteolytic venom designed to subdue insect and small vertebrate prey. Not potent enough to cause serious medical harm to healthy adult humans.
Medical Significance
Harmless to humans. A bite is rare and typically only occurs if the spider is squeezed or trapped against bare skin. Symptoms are usually mild, comparable to a wasp or bee sting, featuring localized pain, redness, and swelling.
Safety Recommendations
No special pest control needed as they are beneficial predators. If encountered indoors, gently capture the spider under a container and release it outdoors near a natural wood or water source.
Habitat & Behavior
Habitat & Range
Found throughout eastern and central North America. Prefers heavily wooded areas, near streams, ponds, swamps, and wetlands, frequently found resting on tree trunks, wooden fences, and dock pilings.
Behavior & Temperament
Nocturnal hunter with a swift and agile running speed. Highly timid when encountered by humans, typically fleeing rapidly to the other side of a tree trunk or dropping to the ground rather than displaying aggression.
Diet & Prey
Generalist predator feeding on insects, tadpoles, small fish, and occasionally aquatic invertebrates, captured by detecting surface vibrations on water or ambushing passing insects on land.
Seasonal Activity
Most active from late spring through early autumn. Mating typically occurs in the early summer, and they overwinter as juveniles or sub-adults under loose bark or in sheltered crevices.
Description
The Dark Fishing Spider is a magnificent and surprisingly gentle giant of the woodland and wetland edges. With its masterful camouflage, it blends seamlessly into the rough bark of trees and weathered wooden docks. Despite its intimidating size and speed, it is a peaceful creature that plays a vital role in regulating aquatic and terrestrial insect populations.
Key Features
Large size, sprawling leg posture, distinctive mottled brown and grey coloration with W-shaped abdominal chevrons, and lack of a web. Differs from wolf spiders by carrying its egg sac in its jaws rather than attached to the spinnerets.
Similar Species
Wolf Spiders (Family Lycosidae) and other fishing spider species like Dolomedes scriptus. Wolf spiders carry their egg sacs attached to the spinnerets, whereas fishing spiders carry them in their mouthparts.
Life Cycle
Females construct a large spherical silk egg sac, carrying it in their jaws until ready to hatch, then building a tent-like nursery web in vegetation where spiderlings molt before dispersing.
Ecological Importance
Serves as an effective top-down predator of insects and small aquatic animals, helping control pest populations while providing an important food source for birds, amphibians, and small mammals.
Conservation Status
Secure and widespread throughout its native range. Not currently evaluated by the IUCN, with stable populations benefiting from wetland preservation.
Interesting Facts
Despite their common name, fishing spiders do not strictly require water and are frequently found deep in upland forests far from any permanent bodies of water, utilizing their aquatic hunting skills opportunistically.
Photography Tips
Use a macro lens with natural side-lighting to highlight the intricate bark camouflage and leg banding. Maintain a calm approach to avoid startling the spider into a rapid escape.
User Notes
Found on log
Identified: 2026-10-04T17:30:57.591233